Rear disc brake conv, master cylinder
 

Im converting my S10 drag truck 12 bolt rear.. with drum brakes on the rear to disc. Due to having strange axles and c-clip elim..im going with stranges rear disk kit.
Im wondering if i need to change my existing brake master cyl.?. Now the setup is a standard chevy master with a proportioning valve.
How do i know if the proportioning valve is setup correctly.? How can i check it? 60/40?

thanks in advance
Keith